1. Field of the Invention
The invention relates to a stabilizer control device that controls the roll rigidity of a stabilizer by an electric motor.
2. Description of the Related Art
When a vehicle turns, the centrifugal force causes roll, which degrades stability. Therefore, vehicles are provided with stabilizers. A stabilizer comprises a stabilizer bar, the central portion of which is fixed to a vehicle body, and the two opposite end portions of which are linked to a suspension. When the vehicle rolls during a turn, the suspension is compressed on the outer wheels and extended on the inner wheels, thus twisting the stabilizer bar. When this occurs, the stabilizer acts as a spring, and a spring reaction force against the twist occurs. Due to this spring reaction force, the stabilizer bar is returned from the twisted state, and the outer wheel side is raised, and the roll is restrained.
In recent years, active stabilizers that actively control the twist and/or return of the stabilizer bar by using electric motors have been developed (see Japanese Patent Application Publication No. JP-A-2005-225301). The active stabilizer comprises stabilizer bars on the left and right sides, and an actuator that is provided between the stabilizer bars. Furthermore, in the active stabilizer, a target control amount is set on the basis of the lateral acceleration representing the roll state of the vehicle, and the like. On the basis of the target control amount, an electric motor of the actuator is driven to perform a twisting control on the stabilizer bars (a control to twist the stabilizer bars from the neutral position), and a return control thereon (a control that returns the stabilizer bars to the neutral position).
However, when an electric motor is used to perform the control, there are restrictions of the electric motor in rotation speed and the like according to the specifications of the electric motor. Therefore, if the vehicle behavior sharply changes so that the target control amount exceeds a limit of the electric motor, the actual rotation of the electric motor fails to follow the target. In addition, if lateral acceleration occurs due to the turning of the vehicle, a command to achieve a target control amount based on the lateral acceleration is output to the electric motor; however, there is a delay before the electric motor can achieve the target control amount in response to the command. Thus, there are cases where the electric motor cannot sufficiently follow a change in vehicle behavior depending on the response performance of the electric motor. Therefore, appropriate roll control may lag the vehicle behavior, causing discomfort to occupants of the vehicle.